The methods used in gear production are in
constant development. In recent years form grinding
(an alternative to the classic meshing grinding)
has become the trend. Another example is a method
used mostly in automotive industry: to improve
theworking life of tools and in order to get tooth form
with higher root strength, gears are produced using
up to three different pre--cutters plus a final honing
or grinding process. One of the latest tendencies in
the development of optimized gears is to apply a
special wave--form--like profile modification during
the finishing process for the reduction of transmission
error.
These production methods require the development
of appropriate calculationmethods. In this paper
the calculation of the resulting tooth form is described
when several tools are used. Then, based
on this tooth form, the effective meshing stiffness
(under load) and the stress calculation are discussed.
The variation of the tooth meshing stiffness during
operation induces a deviation in the rotation--angle
of the output gear from thenominal transmission ratio
(transmission error) causing vibrations and
noise. The meshing stiffness variation can be improved
through optimization of the gear geometry
(transverse contact ratio εα and overlap ratio?εβ),
but the type of profile modification is also very important
for the stiffness under load.
The current calculation method for the tooth resistance
following either AGMA2001 [1] or ISO6336 [2]
is based on the assumption of a tooth form produced
by one tool in a meshing process. Themethod
includes, when using a tool with protuberance,
also a production process with a pre--cutter (with
stock allowance for finishing) and final grinding or
honing process.
This implies that the formulas inAGMA or ISOresistance
calculation methods can not be applied with
gears produced by form grinding or other non--conventional
methods. The problem is that for the calculation calculation
of the tooth root stresses some values such
as tooth thickness and root rounding must be
known. The calculation method assumes that the
tooth formis not exactly known, and therefore presents
formulas which permit calculation of the tooth
form just in the considered section of the tooth.
These formulas assume production through a
meshing process. But in principle, if the tooth formis
given, the tooth can be calculated by directly using
the formulas proposed by the standards. Therefore,
if the tooth form calculation is integrated into the resistance
calculation software, AGMA or ISO standards
can be used for any production method.
AGMA 05FTM04-2005 Referenced Document
ISO 6336-1:1996 Calculation of load capacity of spur and helical gears - Part 1: Basic prinicples, introduction and general influence factors